Voltage balance relay

ABSTRACT

A solid state voltage unbalance relay includes a voltage comparator-sensor means that monitors voltages in different circuits being compared. When an abnormal condition occurs the comparator-sensor produces an output having a polarity indicative of the faulted circuit. Depending upon its polarity, this output is fed to a particular section of a control amplifier that activates contact means connected to a control circuit external to the relay.

United States Patent Waldron Oct. 21, 1975 [541 VOLTAGE BALANCE RELAY Primary ExaminerL. T. Hix I W l l [75] mentor James E a dmn Drexe Hm Pa Attorney, Agent, or Ftrm-Ostrolenk, Faber, Gerb & [73] Assignees: I-T-E Imperial Corporation, Spring s ff House, Pa.

[22] Filed: Apr. 25, 1974 [57] ABSTRACT Appl. No.: 463,889

U.S. Cl... 317/1485 R; 307/235 R; 3l7/DIG. 5 Int. Cl. HOll-l 47/32 Field of Search 307/235 R, 231; 328/146,

328/147; 3l7/D1G. 5, 31,1485 R References Cited UNITED STATES PATENTS 2/1971 Rubner et al 3l7/D1G. 5

A solid state voltage unbalance relay includes a voltage comparator-sensor means that monitors voltages in different circuits being compared. When an abnormal condition occurs the comparator-sensor produces an output having a polarity indicative of the faulted circuit. Depending upon its polarity, this output is fed to a particular section of a control amplifier that activates contact means connected to a control circuit external to the relay.

6 Claims, 2 Drawing Figures yj J5 U.S. Patent Oct. 21, 1975 Sheet 2 of2 3,914,664

VOLTAGE BALANCE RELAY This invention relates to controls for electrical circuits in general and more particularly relates to a solid state voltage balance relay.

In many electrical installations the occurrence of a fault condition in one part of the circuit may cause damage to equipment in another part of the circuit unless remedial action is taken automatically. For example, a blown fuse in a potential transformer circuit resulting in loss of control voltage may cause improper operation of other devices. Thus, it is often necessary to monitor the difference between two voltages so that supervisory action may be taken automatically. In the prior art, this function has been accomplished by an electromechanical relay which has often proven unsatisfactory because of sensitivity to shock and vibration, because of wearing of mechanical parts, and/or because of relatively slow operating times associated with known electromechanical relays.

In order to overcome the disadvantages of an electromechanical voltage balance relay, the instant invention provides a solid state voltage balance relay which includes voltage comparator-sensor means for monitoring and comparing voltages in different circuits. Upon the occurrence of a difference voltage, the comparatorsensor means produces an output that is fed to different sections of a solid state control means, each section of which is actuated by a different polarity output from the comparator-sensor means. Polarity of this output is a function of which voltage source is at the higher potential. Output signals from different sections of the solid state control means are used to control operation of contact means in different output control circuits. Deactuation of the contact means is delayed following restoration of balance voltage conditions.

Accordingly, a primary object of the instant invention is to provide a novel construction for a solid state voltage balance relay means.

Another object is to provide a relay means of this type that is relatively insensitive to shock and vibration.

Still another object is to provide relay means of this type that is fast operating, is compact and will have a relatively long operating life.

These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:

FIG. 1 is a diagram of two circuits being monitored by a solid state voltage balance relay means constructed in accordance with teachings of the instant invention.

FIG. 2 is an electrical schematic of the voltage balance relay of FIG. 1.

Now referring to the figures. In FIG. 1 voltage balance relay is shown connected to conductors a, b, c of voltage source or line A and to conductors a, b, c of voltage source on line B for monitoring the voltages oflines A and B. More particularly, primary windings 13, 14 of potential transformers 11, 11 are connected to conductors a, b, 0' through the respective fuses 12a, 12b, 12c, with fuse 12b being connected to the common connection to primaries I3, 14, fuse 12a being connected to the free end of winding 13, and fuse 120 connected to the free end of winding 14, Secondary winding 16 of potential transformer 11 is connected between relay input terminals 21, 22 and secondary winding connected between relay input terminals 22, 23. Potential transformers 17, 17 and fuses 18a, 18b, 18c connect relay input terminals 24, 25, 26 to the respective conductors c, b, a. Primary 31 of potential transformer 17 is connected through fuses 18b, 180 to conductors b and 0, respectively, and primary 32 of potential transformer 17 is connected through fuses 18a, 18b to the respective conductors a and b. Secondaries 33, 34 of potential transformers 17, 17' are connected between input terminals 24, 25 and 25, 26, respectively.

As will hereinafter be explained in greater detail, the signals appearing between terminals 21, 22 and 24, 25 are fed to the inputs of voltage comparator-sensor 35 whose output is fed to solid state amplifier-controls 43, 44. Outputs of the latter control operation of the respective contacts 45, 46. Contacts 45 are connected across output terminals 39, 40 of relay 10, and contacts 46 are connected across relay output terminals 41, 42. Utilization circuits (not shown) external of relay 10 are connected to output terminals 39, 40 and 41, 42. Input signals applied across terminals 22, 23 and 25, 26 are fed to the inputs of voltage comparator-sensor 36, whose output is fed to both of the solid state amplifier controls 43, 44. Relay 10 is also provided with two additional terminals 27, 28, across which an energizing dc. voltage is applied.

As seen in FIG. 2, the common connection between primaries 48, 49 of transformers 47, 47' is connected to input terminal 22 and the other ends of windings 48, 49 are connected through resistors 188, 189 to the respective input terminals 21, 23. Transformers 47, 47' are provided respectively with secondary windings 51, 52. Similarly, primaries 53, 54 of transformers 55, 55' are both connected to input terminal 25 and the respective winding sections 53, 54 are connected through resistors 193, 194 to the respective input terminals 24, 26. Transformers 55, 55' are provided respectively with secondary windings 56, 57.

Secondary windings 51, 52, 56, 57 provide the inputs for solid state bridge rectifiers 61, 62, 66, 67, respectively. Filter capacitors 71, 72, 76, 77 are connected across the outputs of the respective rectifiers 61, 62, 66, 67. The negative output terminals of rectifiers 61, 62 and the positive output terminals of rectifier 66, 67 are all connected directly to common bus 60 that is referenced to positive input terminal 27 by zener diode 58 and to negative input terminal 28 by zener diode 59. Zener diode 58 is connected through positive bus 80, resistor 64, and diode 65 to terminal 27, and zener diode 59 is connected through negative bus 70, resistor 68, and diode 69 to negative terminal 28. The series combination of filter capacitors 73, 74 is connected between buses and 70.

The positive output terminal of rectifier 61 is connected through potentiometer 78 to the negative output terminal of rectifier 66 and the positive terminal of rectifier 62 is connected through potentiometer 81 to the negative output terminal of rectifier 67. Movable arm 79, 82 of the respective potentiometers 78, 81 are set so that under normal conditions, when the potentials at conductors a, b, c are equal to those at conductors a, b, c, with both being equal to zero as measured to common test point 83 at the respective test points 84, 85, the output at potentiometer arm 79 is fed through reversely connected blocking diodes 86, 87, through the respective resistors 88, 89 to the base for control electrodes of the respective transistors 91, 92.

,These control electrodes are connected to common bus 60 through the respective diodes 93, 94. The base of transistor 91 is also connected through normally open test switch 95 and resistor 96 to negative bu-s70 and the base of transistor 92 is connected through normally open test switch 97 and resistor 98 to positive bus 80.

Transistor-91 is the input stage of a solid state amplifier which also includes transistors 101, 102, 103 that controls power amplifier 104. The output circuittemitter collector) of the latter is connected in series with operating coil 105 for contacts 45. Normally, input amplifier stage 91 is conducting and by so doing maintains transistor 91 is connected through resistor 106 to positive bus 80, and the emitter of transistor 91 is connected through resistor 107 to negative bus 70 and through diode 108 to common bus 60. The collector of transistor 91 is connected directly to the base of transistor 101 whose collector is connected through r'esistors 109, 110 to positive bus 80 and whose emitter is connected directly to common bus 60. The base of transistor 102 is connected to the junction between re-,

sistors 109 and 110, and the emitter of transistor 102. is connected directly to positive bus 80. The collector of transistor 102 is connected through adjustable resistor 111 and fixed resistor 112 to negative bus 70 and is connected through the series combination of resistor 113 and capacitor 114 to common bus 60. The series combination of resistor 115 and diode 116 also con-- nects the collector of transistor 102 to common bus 60. The connecting point between resistor 113 and capacipower amplifier stage 104 cut off. The collector of o trode for input amplifier stage 91 and is connected.

through diode 152-and resistor 89 to the control electrode for input amplifier stage 92. Capacitor 158 isconnected from common bus 60 to the juncture between resistor 88 and diodes 86, 151. Similarly, capacitor 159 is connected from common bus 60 to the juncture between resistor'89 and diodes 87, 152. The series combination of resistor 154 and capacitor 155 is con nected across normally opened contacts 45 to act as an arc'suppressing means. Similarly, the series combina- -:tion of resistor 156 and capacitor 157 is connected across normally opened contacts 46 to act as an arc suppressing means.

In normal operation the voltages at input terminals fied outputsof'rectifier 61 and 66 are equal and the "-'21,22'and 23, 24 areequal just as the voltages at input terminals 22,23 and'25, 26 are equal so that the rectioutputs of rectifier-s 62 and 67 are equal so that zero voltage appears across each of the potentiometers 78 and 81. However, should one of the potential transformer fuses l2a c or 18a-c blow, the voltage associated with the blown fuse decreases and: voltage balance relay 10'will respond by closing one or the other of the control contacts 45, 46. For example, if a fuse 12a-12c tor 114 is connected through diode 1 17 to common bus 1 60. The base of transistor 103 is connected through diode 1 16 to common bus 60 and the emitter of transiscollector of transistor 103 is connected through the series combination of resistors 121, 122 to positive bus- 80 and the connecting point between these resistors is connected to the control electrode of power transistor 104. The collector of transistor 104 is connected to negative bus 70 through the parallel combination of resistor 143 and diode 144.

The emitter of input amplifier transistor 92 is connected through diode 123 to common bus 60 and through resistor 124 to negative bus 70. The collector of transistor 92 is connected through resistors 125, 126 to positive bus 80, and the connecting point between these resistors is connected directly to the base of transistor 127. V

Transistor 92 is the input stage of an amplifier which also includes transistors 127, 128, 129, with the last of these stages 129 being a power stage whose collectoremitter circuit is in series with operating coil 130 which, controls operation of contact 46. The collector of transistor 127 is connected through adjustable resistor 131 and resistor 132 to negative bus 70 and is connected through resistor 133 and capacitor 134 to common bus Y tor 103 is connected directly to common bus 60. The 3 opens, then contacts 'will close, and if one of the fuses18ac opens, then contacts 46 will close. These contacts are used in-conjunction with auxiliary relays, external to relay 10, whose contacts control the operation of alarms and voltage regulating equipment.

More particularly, the voltages appearing at input terminals 21, 22 and 24, 25 are rectified and filtered through transformers 47, 55, bridge rectifiers 61 and 66 and capacitors 71,76. The d.c. outputs of rectifiers 61 and 66 are connected in series opposition through rheostat 78, with the sum of these voltages being measured from movable rheostat arm 79 to reference bus 60. Rheostat 78 is utilized to adjust for small differences'in circuit element impedances and is set so that the voltage sum is zero when the inputs at terminals 21,

' 22iand 24, 25 are balanced. Similarly, another pair of balanced voltages are ordinarily present at input terminals 2'2, 23 and 25, 26, with the output sum of these voltages normally being zero and appearing at rheostat arm 82.

With rectifier output polarities as indicated in FIG. 2, the sum voltage is positive if line A voltage is lower than line B voltage and is negative if the reverse condition exists. If the sum voltage is positive, it is passed by either diode 87 or 152 and if either or both of the sum 7 voltages are positive, all of the amplifier transistors 92,

127, 128, 129 turn on, thereby energizing coil 130 and closing contact 46. Similarly, if the linev B voltage is lower than the line A voltage, the sum voltage at rheo- 60. The junction between resistor 133 and capacitor stat arms 79 or 82 will be negative. Under these circumstances, diode 86 or 151 will conduct and the normally conducting amplifier input transistor 91 will turn off. By so doing the other transistors 101, 102, 103, 104 in this amplifier chain turn on so that coil is energized and closes'contacts 45.

When'system'conditions return to normal, as by replacement of the blown fuse, contacts 45 or 46, as the case may be, open after a time delay. The particular delay is adjustable, and is provided principally by capacitor 134 and adjustable resistor 131 in the case of contacts 46 and by capacitor 114 and adjustable resistor 111 in the case of contact 45. I i

Although in the foregoing preferred embodiments have been discussed, many variations 'an d modifications will now become apparent to those skilled in the art, and .it is therefore understood that this inventionis not limited by the disclosure but only by the appending claims. A

The embodiments of the invention in which an exclusive privilege or property isvclaimed are defined as follows: a

l. A voltage balance solid state relay for continuously monitoring first and second line voltages, said relay comprising:

first isolation means coupled to said first monitored line voltage for providing a first single isolated voltage output proportional to the magnitude of said first monitored voltage;

, second isolation means coupled to said second input monitored line voltage for providing a second single isolated voltage output proportional to the magnitude of said second monitored voltage;

voltage comparator-sensor means coupled to said first and second single isolated voltage outputs for producing an output signal responsive to a voltage difference between said first and second monitored voltages, said voltage comparator-sensor means output being adapted to produce an essentially zero voltage continuous output signal when said first and second monitored voltages are substantially equal, said voltage comparator-sensor means output being further adapted to produce a continuous output signal at a voltage level substantially differing from zero volts and having a first polarity when said first monitored voltage is greater than second monitored voltage and having a second opposed polarity when said monitored voltage is greater than said first monitored voltage; and

first and second solid state control means coupled to said voltage comparator-sensor means output and continuously monitoring said comparator-sensor means output wherein the output of said first solid state control means develops a first control output which is continuously present as long as said comparator-sensor means output is of said first polarity and wherein first control output is absent at all other times and wherein the output of said second solid state control means develops a second control output which is continuously present as long as said comparator-sensor means output is of said second polarity and wherein said second control output is absent at all other times, to thereby provide indications of the relative difference in magnitude of the monitored line voltages.

2. A voltage balance solid state relay as set forth in claim 1, wherein said first isolation means includes first transformer means having a single primary winding coupled to said first monitored line voltage and a single secondary winding, and first rectifier means coupled to said first single secondary winding for producing a first secondary winding for producing a second single d.c. output voltage proportional to the magnitude of said second monitored voltage; and said voltage comparator-sensor means includes first circuit means connecting said first and second single d.c. output voltages in opposition for producing a dc. voltage difference, said first circuit means including a first adjustable member coupled to said 'voltage comparator-sensor means, whereby said voltage comparator-sensor means output signal is set to said zero voltage continuous signal responsive to said first and second monitored voltages being equal.

3. A voltage balance solid staterelay as set forth in claim 1, further including first and second delay means respectively operatively coupled to said first and second solid state control means for independently delaying the cessation of said first continuous control output in the event the output of said voltage comparatorsensor means returns to an essentially zero voltage condition responsive to the cessation of an unbalanced condition between said first and second monitored voltages.

4. A voltage balance solid state relay as set forth in claim 1, further including third isolation means coupled to a third line voltage to be monitored for providing a third single isolated voltage output proportional to the magnitude of said third monitored voltage;

fourth isolation means coupled to fourth line voltage to be monitored for providing a fourth single isolated voltage output to the magnitude of said fourth monitored voltage;

another voltage comparator-sensor means coupled to said third and fourth single isolated voltage outputs for producing another output signal responsive to a voltage difference between said third and fourth monitored voltages, said another voltage comparator-sensor means output also being adapted to produce said essentially zero voltage continuous output signal when said third and fourth monitored voltages are substantially equal, said another voltage comparator-sensor means output being further adapted to produce said non-zero voltage continuous output signal and having said first polarity when said third monitored voltage is greater than said fourth monitored voltage and having said second opposed polarity when said fourth monitored voltage is greater than said third monitored voltage; and

said first and second solid state control means also being coupled to said another voltage comparatorsensor means output and also continuously monitoring said another comparator-sensor means output wherein said first solid state control means output also develops said first control output which is also continuously present as long as said another comparator-sensor means output is of said first polarity and wherein said second solid state control means output also develops said second control output which is also continuously present as long as said another comparator-sensor means output is of said second polarity, to thereby provide indications of the relative difference in magnitude of both the first and second and the third and fourth monitored line voltages.

5. A voltage balance relay as set forth in claim 4, wherein said third isolation means includes third transformer means having a single primary winding coupled to said third monitored line voltage and a single secondary winding, and third rectifier means coupled to said third single secondary winding for producing a third single d.c. output voltage proportional to the magnitude of said third monitored voltage; said fourth isolation means includes fourth transformer means having a single primary winding coupled to said fourth monitored line voltage and a single secondary winding, and

fourth rectifier means coupled to said fourth single secondary winding for producing a fourth single do. out put voltage proportional to the magnitude of said fourth monitored voltage; and said another voltage comparator-sensor means includes secon circuit means connecting said third and fourth single d.c. output voltages in opposition for producing a dc. voltage difference, said second circuit means including a second adjustable member coupled to said another voltage com parator-sensor means, whereby said another voltage comparator-sensor means output signal is set to said zero voltage continuous signal responsive to said third and fourth monitored voltages being equal.

6. A voltage balance solid state relay as set forth in claim 4, further including first and second delay means respectively operatively coupled to said first and sec ond solid state control means for independently delaying the cessation of said first continuous control output in the event the output of said another voltage com parator-sensor means returns to an essentially zero voltagecondition responsive to the cessation of an unv.

itored voltages. 

1. A voltage balance solid state relay for continuously monitoring first and second line voltages, said relay comprising: first isolation means coupled to said first monitored line voltage for providing a first single isolated voltage output proportional to the magnitude of said first monitored voltage; second isolation meaNs coupled to said second input monitored line voltage for providing a second single isolated voltage output proportional to the magnitude of said second monitored voltage; voltage comparator-sensor means coupled to said first and second single isolated voltage outputs for producing an output signal responsive to a voltage difference between said first and second monitored voltages, said voltage comparator-sensor means output being adapted to produce an essentially zero voltage continuous output signal when said first and second monitored voltages are substantially equal, said voltage comparatorsensor means output being further adapted to produce a continuous output signal at a voltage level substantially differing from zero volts and having a first polarity when said first monitored voltage is greater than second monitored voltage and having a second opposed polarity when said monitored voltage is greater than said first monitored voltage; and first and second solid state control means coupled to said voltage comparator-sensor means output and continuously monitoring said comparator-sensor means output wherein the output of said first solid state control means develops a first control output which is continuously present as long as said comparator-sensor means output is of said first polarity and wherein first control output is absent at all other times and wherein the output of said second solid state control means develops a second control output which is continuously present as long as said comparator-sensor means output is of said second polarity and wherein said second control output is absent at all other times, to thereby provide indications of the relative difference in magnitude of the monitored line voltages.
 2. A voltage balance solid state relay as set forth in claim 1, wherein said first isolation means includes first transformer means having a single primary winding coupled to said first monitored line voltage and a single secondary winding, and first rectifier means coupled to said first single secondary winding for producing a first single D.C. output voltage proportional to the magnitude of said first monitored voltage; said second isolation means includes second transformer means having a single primary winding coupled to said second monitored line voltage and a single secondary winding, and second rectifier means coupled to said second single secondary winding for producing a second single d.c. output voltage proportional to the magnitude of said second monitored voltage; and said voltage comparator-sensor means includes first circuit means connecting said first and second single d.c. output voltages in opposition for producing a d.c. voltage difference, said first circuit means including a first adjustable member coupled to said voltage comparator-sensor means, whereby said voltage comparator-sensor means output signal is set to said zero voltage continuous signal responsive to said first and second monitored voltages being equal.
 3. A voltage balance solid state relay as set forth in claim 1, further including first and second delay means respectively operatively coupled to said first and second solid state control means for independently delaying the cessation of said first continuous control output in the event the output of said voltage comparator-sensor means returns to an essentially zero voltage condition responsive to the cessation of an unbalanced condition between said first and second monitored voltages.
 4. A voltage balance solid state relay as set forth in claim 1, further including third isolation means coupled to a third line voltage to be monitored for providing a third single isolated voltage output proportional to the magnitude of said third monitored voltage; fourth isolation means coupled to fourth line voltage to be monitored for providing a fourth single isolated voltage output to the magnitude of said fourth monitored voltage; another voltage comparator-sensor means coupled to said third and fourth single iSolated voltage outputs for producing another output signal responsive to a voltage difference between said third and fourth monitored voltages, said another voltage comparator-sensor means output also being adapted to produce said essentially zero voltage continuous output signal when said third and fourth monitored voltages are substantially equal, said another voltage comparator-sensor means output being further adapted to produce said non-zero voltage continuous output signal and having said first polarity when said third monitored voltage is greater than said fourth monitored voltage and having said second opposed polarity when said fourth monitored voltage is greater than said third monitored voltage; and said first and second solid state control means also being coupled to said another voltage comparator-sensor means output and also continuously monitoring said another comparator-sensor means output wherein said first solid state control means output also develops said first control output which is also continuously present as long as said another comparator-sensor means output is of said first polarity and wherein said second solid state control means output also develops said second control output which is also continuously present as long as said another comparator-sensor means output is of said second polarity, to thereby provide indications of the relative difference in magnitude of both the first and second and the third and fourth monitored line voltages.
 5. A voltage balance relay as set forth in claim 4, wherein said third isolation means includes third transformer means having a single primary winding coupled to said third monitored line voltage and a single secondary winding, and third rectifier means coupled to said third single secondary winding for producing a third single d.c. output voltage proportional to the magnitude of said third monitored voltage; said fourth isolation means includes fourth transformer means having a single primary winding coupled to said fourth monitored line voltage and a single secondary winding, and fourth rectifier means coupled to said fourth single secondary winding for producing a fourth single d.c. output voltage proportional to the magnitude of said fourth monitored voltage; and said another voltage comparator-sensor means includes secon circuit means connecting said third and fourth single d.c. output voltages in opposition for producing a d.c. voltage difference, said second circuit means including a second adjustable member coupled to said another voltage comparator-sensor means, whereby said another voltage comparator-sensor means output signal is set to said zero voltage continuous signal responsive to said third and fourth monitored voltages being equal.
 6. A voltage balance solid state relay as set forth in claim 4, further including first and second delay means respectively operatively coupled to said first and second solid state control means for independently delaying the cessation of said first continuous control output in the event the output of said another voltage comparator-sensor means returns to an essentially zero voltage condition responsive to the cessation of an unbalanced condition between said third and fourth monitored voltages. 